This invention relates to a copy sheet feed device for an electrophotographic copying apparatus.
Methods of forming a duplicate image on each copy sheet by an electrophotographic copying apparatus may be broadly classified into the following according to differences in method steps:
1. A method wherein an optical image of an original formed by means of an optical system is converted into an electrostatic latent image on a photoreceptor including a photoconductive material layer which latent image is developed into a visible image by means of a toner containing developing agent to produce a duplicate of the original; PA1 2. A method wherein a picture signal is recorded as an electrostatic latent image on a recording medium including a dielectric layer by scanning with an electrode, and the latent image is developed into a visible image to produce a duplicate of the original in the same manner as described with reference to paragraph 1; PA1 3. An electrostatic latent image produced as described in paragraphs 1 and 2 is transferred to another recording medium and then developed into a visible image by means of a toner containing developing agent to produce a duplicate of the original; and PA1 4. A method wherein a visible image produced as described in paragraphs 1, 2 and 3 is transferred to paper or other transfer-printing sheet to produce a duplicate of the original.
Various proposals have been made to increase the degree of precision with which copying of an original can be controlled in electrophotographic copying apparatus wherein copying is carried out by the aforementioned methods. One of such proposals is that the photoreceptor of paragraph 1, the recording medium of paragraphs 2 and 3 and the copy sheet or other supporter of the final image (hereinafter referred to as a copy sheet) should be made to carry the image in a position which corresponds to the position of the image in the original, irrespective of the method steps involved.
To attain the end of precluding deviation of the image on the carrier from its correct position, it has hitherto been customary to provide means whereby initiation of movement of an original scanning system, (which is a scanning optical system in the case where the original is stationary and which is a movable original rest in the case where the optical system is stationary) is synchronized to the initiation of feeding of a copy sheet as by successively depressing command switches by a cam rotating at a constant speed to effect control of associated parts. This means has a disadvantage in that, because of its relatively large inertia, the original scanning system is not necessarily restored to its original starting position or zero point in the strict sense of the term, thereby making it impossible to attain full synchronization at all times.
In order to obviate this problem, improvements should be incorporated in means for moving and stopping the original scanning system so as to increase the degree of precision with which synchronization can be effected. However, this has the disadvantage of a copying apparatus being increased in cost or lowered in reliability in performance due to variations in the precision with which the component parts are finished.